How to get Elastic Container Repository URI from Cloud Formation?

Question

I'm trying to create an Elastic Container Service (ECS) setup from Cloud Formation.

However I don't want the ECS repository to have the ugly autogenerated URI:

111111111.dkr.ecr.us-east-1.amazonaws.com/docker-repo.company.com

but instead I want it to have a nice and shiny

docker-repo.company.com

The repository itself does not allow setting the URI or even a CNAME. So I'm trying to setup a S3 bucket to redirect to the repo. However unless I'm missing something, Cloud Formation doesn't support this since using !Ref or !GetAtt there's nothing I can query in the AWS::ECR::Repository object that will give me the repository URI.

Am I missing something? Thanks!

True, but what would be the point if we plan on using ECS anyway? This way AWS manages it for us, we minimize the number of services we have to manage ourselves. — oblio
Yeah, only if the requirements that fall outside the specific setup of an ECR are worth it to you. — Matt

oblio oblio · Accepted Answer · 2017-08-24T10:15:24

This is kind of silly, but in the end it seems you cannot refer to the URI of an ECR because Cloud Formation doesn't support it.

There's no attribute for the URI, even though funnily enough their Ruby SDK does support it and even the third-party, cross-cloud Terraform supports it.

However, you can hack around this because the repository URI is stable, it doesn't contain any random part, so you can compose the URI from things you already have:

HostName: !Sub "${AWS::AccountId}.dkr.ecr.${AWS::Region}.amazonaws.com/${dockerrepocompanycom}"

or for the less cool, old-school version:

HostName: !Join [ ".", [ !Ref "AWS::AccountId", "dkr.ecr", !Ref "AWS::Region", !Join [ "/", [ "amazonaws.com", !Ref "dockerrepocompanycom" ] ] ] ]

Full working configuration for creating the S3 bucket:

   s3dockerrepo1redirect:
    Type: AWS::S3::Bucket
    Properties:
        BucketName: "docker-repo.company.com"
        WebsiteConfiguration:
            RedirectAllRequestsTo:
               HostName: !Sub "${AWS::AccountId}.dkr.ecr.${AWS::Region}.amazonaws.com/${dockerrepocompanycom}"

How to get Elastic Container Repository URI from Cloud Formation?

2 Answers